man3type/size_t.3type

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   7 .TH SIZE_T 3type 2022-07-20 "Linux man-pages (unreleased)" "Linux Programmer's Manual"
   8 .SH NAME
   9 size_t, ssize_t \- count of bytes
  10 .SH LIBRARY
  11 Standard C library
  12 .RI ( libc )
  13 .SH SYNOPSIS
  14 .nf
  15 .B #include <stddef.h>
  16 .PP
  17 .BR typedef " /* ... */  " size_t;
  18 .PP
  19 .B #include <sys/types.h>
  20 .PP
  21 .BR typedef " /* ... */  " ssize_t;
  22 .fi
  23 .SH DESCRIPTION
  24 .TP
  25 .I size_t
  26 Used for a count of bytes.
  27 It is the result of the
  28 .IR sizeof ()
  29 operator.
  30 It is an unsigned integer type
  31 capable of storing values in the range
  32 .RB [ 0 ,
  33 .BR SIZE_MAX ].
  34 .TP
  35 .I ssize_t
  36 Used for a count of bytes or an error indication.
  37 It is a signed integer type
  38 capable of storing values al least in the range
  39 .RB [ \-1 ,
  40 .BR SSIZE_MAX ].
  41 .SS Use with printf(3) and scanf(3)
  42 .TP
  43 .I size_t
  44 The length modifier for
  45 .I size_t
  46 for the
  47 .BR printf (3)
  48 and the
  49 .BR scanf (3)
  50 families of functions is
  51 .BR z ,
  52 resulting commonly in
  53 .B %zu
  54 or
  55 .B %zx
  56 for printing
  57 .I size_t
  58 values.
  59 .TP
  60 .I ssize_t
  61 Glibc and most other implementations provide a length modifier for
  62 .I ssize_t
  63 for the
  64 .BR printf (3)
  65 and the
  66 .BR scanf (3)
  67 families of functions,
  68 which is
  69 .BR z ;
  70 resulting commonly in
  71 .B %zd
  72 or
  73 .B %zi
  74 for printing
  75 .I ssize_t
  76 values.
  77 Although
  78 .B z
  79 works for
  80 .I ssize_t
  81 on most implementations,
  82 portable POSIX programs should avoid using it\(emfor example,
  83 by converting the value to
  84 .I intmax_t
  85 and using its length modifier
  86 .RB ( j ).
  87 .SH VERSIONS
  88 .TP
  89 .I size_t
  90 .IR <aio.h> ,
  91 .IR <glob.h> ,
  92 .IR <grp.h> ,
  93 .IR <iconv.h> ,
  94 .IR <mqueue.h> ,
  95 .IR <pwd.h> ,
  96 .IR <signal.h> ,
  97 and
  98 .I <sys/socket.h>
  99 define
 100 .I size_t
 101 since POSIX.1-2008.
 102 .TP
 103 .I ssize_t
 104 .IR <aio.h> ,
 105 .IR <mqueue.h> ,
 106 and
 107 .I <sys/socket.h>
 108 define
 109 .I ssize_t
 110 since POSIX.1-2008.
 111 .SH STANDARDS
 112 .PD 0
 113 .IR size_t :
 114 C99 and later;
 115 POSIX.1-2001 and later.
 116 .PP
 117 .IR ssize_t :
 118 POSIX.1-2001 and later.
 119 .PD
 120 .SH NOTES
 121 .TP
 122 .I size_t
 123 The following headers also provide
 124 .IR size_t :
 125 .IR <aio.h> ,
 126 .IR <glob.h> ,
 127 .IR <grp.h> ,
 128 .IR <iconv.h> ,
 129 .IR <monetary.h> ,
 130 .IR <mqueue.h> ,
 131 .IR <ndbm.h> ,
 132 .IR <pwd.h> ,
 133 .IR <regex.h> ,
 134 .IR <search.h> ,
 135 .IR <signal.h> ,
 136 .IR <stdio.h> ,
 137 .IR <stdlib.h> ,
 138 .IR <string.h> ,
 139 .IR <strings.h> ,
 140 .IR <sys/mman.h> ,
 141 .IR <sys/msg.h> ,
 142 .IR <sys/sem.h> ,
 143 .IR <sys/shm.h> ,
 144 .IR <sys/socket.h> ,
 145 .IR <sys/types.h> ,
 146 .IR <sys/uio.h> ,
 147 .IR <time.h> ,
 148 .IR <unistd.h> ,
 149 .IR <wchar.h> ,
 150 and
 151 .IR <wordexp.h> .
 152 .TP
 153 .I ssize_t
 154 The following headers also provide
 155 .IR ssize_t :
 156 .IR <aio.h> ,
 157 .IR <monetary.h> ,
 158 .IR <mqueue.h> ,
 159 .IR <stdio.h> ,
 160 .IR <sys/msg.h> ,
 161 .IR <sys/socket.h> ,
 162 .IR <sys/uio.h> ,
 163 and
 164 .IR <unistd.h> .
 165 .SH SEE ALSO
 166 .BR read (2),
 167 .BR readlink (2),
 168 .BR readv (2),
 169 .BR recv (2),
 170 .BR send (2),
 171 .BR write (2),
 172 .BR fread (3),
 173 .BR fwrite (3),
 174 .BR memcmp (3),
 175 .BR memcpy (3),
 176 .BR memset (3),
 177 .BR offsetof (3),
 178 .BR ptrdiff_t (3type)